Re: [PATCH v3 1/3] cgroup/cpuset: Reject updates that empty the top sched domain

[Ridong Chen <ridong.chen@linux.dev>]

On 11/10/2026 1:03 PM, Guopeng Zhang wrote:
> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
> 
> Boot-isolated CPUs remain in top_cpuset.effective_cpus, but are excluded
> from its scheduling domain by generate_sched_domains(). Checking only
> effective_cpus when distributing CPUs to partitions can therefore allow
> all boot domain housekeeping CPUs to be taken from the top cpuset.
> 
> The resulting empty domain triggers a warning in build_sched_domains()
> and can cause an out-of-bounds CPU access in build_perf_domains(). Both
> root and isolated partitions can trigger this, whether local or remote.
> For example, on a 32-CPU system booted with isolcpus=domain,10-31:
> 
>    echo 0-9 > A/cpuset.cpus
>    echo root > A/cpuset.cpus.partition
>    Oops: general protection fault
>    RIP: 0010:build_perf_domains+...
> 
> Require local and remote partition creation and CPU mask updates to
> leave an active boot domain housekeeping CPU in the top cpuset,
> accounting for CPUs returned by the same update.
> 
> Add test cases to test_cpuset_prs.sh to verify that every partition
> update leaves an active boot domain housekeeping CPU in the top cpuset.
> 
> Fixes: 9b496a8bbed9 ("cgroup/cpuset: Prevent leakage of isolated CPUs into sched domains")
> Co-developed-by: Ridong Chen <ridong.chen@linux.dev>
> Signed-off-by: Ridong Chen <ridong.chen@linux.dev>

It would be better with: Ridong Chen <chenridong@xiaomi.com>

-- 
Best regards
Ridong